In typical polyolefin reaction processes, various components are added to a polymerization system to begin the polyolefin reaction process. These various components can include olefin feed components, diluent components, and catalyst components.
Upon introduction of the olefin feed components, the diluent components, and the catalyst components into a polymerization reactor, the polymerization reaction process begins. The polymerization reaction takes place within the polymerization reactor under a set of reaction conditions. The reaction conditions can include reaction temperature, reaction pressure, reactor residence time, and concentrations of the various components within the reactor, such as reactor solids, ethylene, hexene, hydrogen, co-catalysts, antistatic agents, electron donors, and inerts, such as ethane and propane.
It is often desirable to produce polyolefins having certain physical and mechanical properties, depending upon the application and market in which the polyolefin is to be used. These markets can include, for example, blow molding, injection molding, rotational molding, film, drums, and pipe. Some physical properties that can be important, depending on the product requirement and application, are molecular weight, molecular weight distribution, density, crystallinity, and rheology. Some mechanical properties that can be important, depending on the product requirement and application, are modulus, tensile properties, impact properties, stress relaxation, creep, and elongation. However, obtaining polyolefins with consistent desired properties is difficult to accomplish. The properties of the polyolefin produced within the polymerization system can be affected by the reaction conditions under which the reaction takes place, including reactor concentrations. Consequently, specific control of the various components introduced into the reactor, including catalyst components, must often be precisely measured and monitored.
The rate at which catalyst components are added to the reactor can affect the physical and mechanical properties of the polyolefin being produced within the reactor, and therefore is an important factor to control and monitor. Conventional methods of adding catalyst components to reactor systems may introduce possible error into the reaction process, resulting in the production of off-specification product. For example, in at least one conventional polyolefin reaction system, catalyst components are fed to the polymerization reactor using ball check feeders. Ball check feeders typically include a rotating cylinder having a cavity on one side of the cylinder. The cavity fills with catalyst components and empties the catalyst components into the reactor after each 180° rotation of the cylinder. However, the amount of catalyst component that fills the cavity during each rotation of the cylinder may be inconsistent, resulting in inconsistent feed of catalyst components to the reactor. Inconsistent feed of catalyst components (as well as other components) to the reactor can cause inconsistent operation and control of the polymerization reaction process, resulting in highly variable production rates and production of product outside the desired specification limits.
Despite existing systems and methods to control the feed of catalyst and polymer components to polymerization systems, a need exists for improved systems and methods for controlling the introduction of multiple components to a polymerization reactor. Further, a need also exists for improved systems and methods for combining multiple components in a polymerization system. Yet another need exists for improved systems and methods of feed control for a catalyst component in a polymerization process. Another need exists for improved systems and methods to produce a polymer.